PONE-D-20-14779

Differential effects of visual versus auditory biofeedback training for postural control

PLOS ONE

Dear Dr. Asaka,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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Dear authors,

Despite one reviewer suggested acceptation, there are important concerns indicated by second reviewer. The authors need to improve introduction rationality and results presentation (improve the writing and sequence). Both aspects are important to consider the manuscript for publication. 

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Fabio A. Barbieri, PhD

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The goal of this study was to determine if discrete auditory feedback during a body sway targeting task improved performance more than discrete visual feedback. The study was well designed, the methods were appropriate, and the manuscript is well written. The strengths of the paper include (1) random assignment of participants to two groups, and (2) the use of both spatial and temporal measures to assess performance. There are a few minor issues and one curiosity (#5) listed below. I would like to commend the authors for this work – it was a please to review this article. Overall, this manuscript is relevant and will be of interest to a wide range of researchers and clinicians.

Minor Issues:

1. Avoid acronyms, especially in the introduction/discussion – using the word feedback rather than BF doesn’t take much more space.

2. Line 373 – The results of the study are not simply ‘suggestive’, given the randomized trial, it was demonstrated that auditory feedback was more effective than visual feedback for the swaying task.

3. I recommend the authors reconsider the text on lines 315-317. Being the first to conduct an experiment is not relevant; adding knowledge to the field is relevant. If the authors choose to keep the wording about being first, I recommend they state they were the first to demonstrate that discrete auditory feedback was more effective at improving performance and learning (assuming no one else has demonstrated this).

4. Line 81 – extra ‘e’

5. This is a question I have, which may or may not be relevant for the text. Is there any indication that visual or auditory feedback have different cognitive demands? I would predict that, at least initially, auditory feedback would be more challenging due to the transformation of volume and pitch into sway magnitude and direction, whereas visual feedback does not (apparently) need to be transformed. Perhaps this distinction is related to improved learning – the auditory may be more attention-demanding, which may promote learning.

Reviewer #2: The present manuscript investigated the effectiveness of discrete visual versus auditory biofeedback (BF) to improve a postural tracking task. Twenty-two young participants were assigned to either a visual or auditory BF group. Participants were asked to shift their center of pressure (CoP) by voluntarily swaying forward and backward following a hidden, moving in a sinusoidal fashion and displayed intermittently. Results showed that, according to the authors, auditory BF was better than visual BF improving spatial and temporal relationship between CoP and target positioning. Based upon these results it was concluded that motor learning of postural control was improved by discrete auditory BF training.

Overall, the manuscript focuses on an important issue, which is related to improvement of postural positioning in a tracking task under different sensory cues displayed intermittently. The design and procedures seem to be sound, although a few and important issues still need to be clarified. Also the results and interpretation need to further explained. As a consequence, there a few issues that, as reviewer who is reading the manuscript for the first time, I would like to point out.

The first issue that needs to be revised and/or further clarified in the manuscript is the idea of “training for postural control”. Such usage does not reflect the essence of what is training. In my opinion, the training focuses on one particular behavior of tracking, visual or auditory, intermittent target. The movement involving the whole body is nominated, correctly, as postural control, but there is no measure or intention (at least from my view) of measuring postural control performance other than following the target. Using the broader scope such as training for postural control might furnish an equivocal idea that the training is towards improvement of postural control as a daily use task. Certainty, this is not the case and the manipulation and results cannot be used for such usage. Thus, there is the need to clarify and better refer, throughout the manuscript and including the title, to the task involved in the study rather than generalize as “postural control”.

Second, introduction needs to be improved in order to justify the rationality of the study. Why training effects would be potentially different between visual and auditory BF? Such clarification seems to be important even for preparing the reader for the proposed hypothesis. I am still wondering why was hypothesized that intermittent auditory BF would lead to learning but not visual BF. Yet, such learning effect would occur only in the temporal domain. Please further develop rationality for each of these issues even to support any discussion regarding the observed results.

Procedures seem to be sound, but there is the need to further describe the conditions and instructions for the participants. Regarding the conditions, when the stimulus was auditory, participants had visual cues available? When participants were performing the visual training, auditory cues from the environment were available. A detailed description regarding the available cues is critical in order to further understand and discuss possible differences between sensory cues.

Results are hard to follow, mainly for a couple of reasons. First, please refer in the text, because present the results where the reader can find the data. Refer to the Figure that the reader could see the results. Second, please clarify the statistical notation. It seems that statistical notation for auditory results are presented in the superior portion of the plot and for vision in the inferior part of it (I am not sure about this). For example, Figure 5B visual was not significant, but the note is nearby the symbol. On the other hand, auditory BF was significant and there is the notation indicating “NS”.

Finally, I do not agree with the interpretation and conclusion that only auditory BF improved postural tracking. In this case, there are a few aspects that must be clarified. My first concern is regarding the use and interpretation of the variables employed in the study. From my understanding, the most important variable indicating if the task was accomplished is the average and SD of distance (even mentioned – line 193-194). The mean peak difference is the error at the time interval of BF. Thus, data show that both sensory cues were used to improve the tracking, but more erratically in the visual condition. Such difference is even noticed in the coherence values (lower values for the visual – moving the body less coherent with the stimulus) and in the phase (higher values for the visual – moving lagging behind the stimulus). These are the different strategies that participants adopted in using different sensory cues. The question is why participants adopt these different strategies? Is the visual processing slower than the auditory? Is visual used more likely a confirmatory cue? In my point of view, the manuscript should discuss and clarify these issues, but not saying the visual training did not improve postural tracking because it did (at least from what I could get from Figure 4). Finally, I did not understand the usage of the correlation analysis. Yet, the number of participants and the obtained results do not allow for a clear cut interpretation of this possible relationship. Why does use it?

Minor issue:

- Please revise abstract, reducing its size and presenting results and conclusion properly

- Line 59-60: statement here contradicts the following sentence (lines 61-63). Please revise.

- Hypothesis must be justified.

- Please reference Figures in the text, before presenting results.

- Figure 1 is hard to follow with those boxes “WithBF” and “WithoutBF”.

- Please revise statistical notation in the Figures

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Reviewer #1: No

Reviewer #2: No

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Differential effects of visual versus auditory biofeedback training for voluntary postural sway

PONE-D-20-14779R1

Dear Dr. Asaka,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Fabio A. Barbieri, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: The revised version of the manuscript has been improved with all the suggested changes made. The authors also, based upon the suggestions from the reviewers, made substantial changes in the presentation and, most importantly, in the interpretation of the results, contributing significantly to the knowledge in the field. Thus, I congratulate with the authors for the submission and the presented manuscript.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: Yes: Jose A. Barela